Why?
I know that is not necessary for joomla, but I have another systems integrated in joomla and some of this use parameters with spaces in url and getBase returns this spaces in <base> tag.
Example:
<base href="http://www.sitename.com/page-Vatra Dornei-ln1.html" />
where "Vatra Dornei" is an argument for a parameter that is used in system integrated by me.